In recent years, MPLS (Multi-Protocol Label Switching) that manages network paths by applying the label switching to IP (Internet Protocol) networks has come into wide use. Further, GMPLS (Generalized Multi-Protocol Label Switching) which can be applied not only to IP networks, but also to time division multiplexing networks, such as SDH (Synchronous Digital Hierarchy)/SONET (Synchronous Optical NETwork) and other networks, such as wavelength division multiplexing networks, has been commercially implemented. The description given herein deals with, as an example, a communication network in which paths are set up by using GMPLS.
FIG. 1 is a diagram illustrating an example of a path generation sequence in GMPLS. In the example of FIG. 1, path generation (signaling) is performed to set up a path from a start point node N1 to an endpoint node N4. In this patent specification, the start point node N1 which provides an entrance to a communication network for the path to be set up may be referred to as the ingress node. Similarly, the endpoint node N4 which provides an exit from the communication network for the path to be set up may be referred to as the egress node.
First, the start point node N1 transmits a path message “PathMsg”, a request message for requesting the reservation of a path setup, to its adjacent node N2. In the PathMsg, the start point node N1 specifies ERO (Explicit_Route Object), i.e., routing information for the path to be set up from the start point node N1 to the endpoint node N4, and a label that the node N1 intends to use between it and the node N2.
At the node N2, if the label specified in the received PathMsg is not in use, the label is set to a reserved state. The node N2 then transmits a similar PathMsg to the next intermediate node N3. The node N3 performs the same processing as the node N2, and transmits the PathMsg to the endpoint node N4.
Then, at the node N4, if the path requested by the received PathMsg can be set up, the node N4 returns a reserve message “ResvMsg”. The reserve message corresponds to a response message delivered to notify that the reservation of the path requested by the PathMsg is completed. After transmitting the ResvMsg, the node N4 sets up a cross connect in the endpoint node N4 in order to generate the path requested by the PathMsg.
The node N3 that received the ResvMsg from the endpoint node N4 sets up a cross connect in the node N3 so that the requested path is generated, and forwards the ResvMsg to the node N2. The same processing is performed at the nodes N2 and N1, and the path setup between the node N1 and the node N4 is completed.
FIG. 2 is a diagram illustrating the data structure of the path message. In the figure, the fields (objects) which are not hatched are optional objects. This convention also applies to the data structures illustrated in FIGS. 3 and 22 hereinafter given. A brief description of the data carried in the PathMsg is given below.
SESSION, SENDER_TEMPLATE: Fields for storing connection identification information, the path being made uniquely identifiable by combining five kinds of information (ingress address, egress address, tunnel ID, LSP ID, and extended tunnel ID).
RSVP_HOP: Stores the local ID of the path message PathMsg transmitting node as identification information for the fiber used.
TIME_VALUES: A field for storing path refresh interval, i.e., refresh timer length.
EXPLICIT_ROUTE: A field for storing routing information specifying a route along which the path is to be routed.
LABEL_REQUEST: A field for storing the type of the requested label.
PROTECTION: A field for storing the kind, etc. of the protection that the path requests.
SESSION_ATTRIBUTE: A field for storing the name of the path, etc.
ADMIN_STATUS: A field for storing special information such as Admin_Down and Deletion.
SENDER_TSPEC: A field for storing rate information (2.5G, 10G, etc.) that the path requests.
UPSTREAM_LABEL: A field for storing the reserved label information (information for identifying wavelength).
ALARM_SPEC: A field for storing the kind and time of alarm generation.
NOTIFY_REQUEST: An object used to request the transmission of a NotifyMsg (to be described later) when a failure occurs on the requested path.
FIG. 3 is a diagram illustrating the data structure of the reserve message ResvMsg. A brief description of the data carried in the ResvMsg is given below.
RESV_CONFIRM: A field for storing information used when requesting the transmission of a ResvConfMsg.
FLOWSPEC: A field for storing the same connection identification information as that stored in the SENDER_TEMPLATE object carried in the PathMsg.
FILTERSPEC: A field for storing the requested rate information, as in the SENDER_TSPEC object carried in the PathMsg.
LABEL: A field for storing the label information, as in the UPSTREAM_LABEL object carried in the PathMsg.
ALARM_SPEC: A field for storing the type and time of alarm generation.
NOTIFY_REQUEST: An object used to request the transmission of the NotifyMsg (to be described later) when a failure occurs on the requested path.
On the other hand, in packet communications, RPR (Resilient Packet Ring) is defined in IEEE 802.17 as a ring network topology that provides enhanced fault tolerance while using SONET as a communication network. FIG. 4 is a diagram illustrating an example of an RPR network.
The RPR network 200 includes a dual-ring transmission line constructed from two transmission lines, a 0-numbered transmission line 201 (ringlet 0) and a 1-numbered transmission line 202 (ringlet 1), and node apparatuses 203A to 203D inserted in these transmission lines. The clockwise-rotating ringlet is called the ringlet 0, and the counterclockwise-rotating ringlet is called the ringlet 1.
The node apparatuses 203A to 203D connect the RPR network 200 to external networks 204A to 204D, respectively. The RPR network 200 relays the transmission/reception of frames among the external networks 204a to 204A. In the following description, the direction in which each node apparatus transmits data out onto the ringlet 0 may be referred to as the east, and the direction in which each node apparatus transmits data out onto the ringlet 1 may be referred to as the west.
FIG. 5 is a diagram illustrating a condition in which a cross connect that matches a path forming the RPR network is set within each node apparatus equipped with an RPR unit. Solid line 205 indicates a transmission line in the communication network, and semi-dashed line 206 indicates a ring-shaped network which forms the RPR network. The transmission line 205 includes, for example, an optical fiber for transmitting data in the clockwise direction in the figure and an optical fiber for transmitting data in the counterclockwise direction.
To form the ring-shaped network 206, a line interface unit (LIU) 101, to which a line connecting to a node adjacent in the east direction is connected, and a line interface unit 102, to which a line connecting to a node adjacent in the west direction is connected, are used in the node apparatus 203A. Likewise, a line interface unit 111, to which a line connecting to a node adjacent in the east direction is connected, and a line interface unit 112, to which a line connecting to a node adjacent in the west direction is connected, are used in the node apparatus 203B.
The node apparatus 203A includes an RPR unit 103. The RPR unit 103 encapsulates the frame received from the external network 204A and inserts (adds) the encapsulated RPR frame into the network 206. Further, the RPR unit 103 removes (drops) an RPR frame flowing in the network 206, decapsulates it, and transmits the decapsulated frame into the external network 204A. Similarly, the node apparatus 203B includes an RPR unit 113.
In the node apparatus 203A, a path is set between the line interface unit 101 and the RPR unit 103 by a cross connect set up by a switch 104. Likewise, a path is set between the line interface unit 102 and the RPR unit 103 by a cross connect set up by the switch 104.
In the node apparatus 203B also, a switch 114 is provided to set up a cross connect between the line interface unit 111 and the RPR unit 113 and a cross connect between the line interface unit 112 and the RPR unit 113. The cross connects set up by the switches 104 and 114 are indicated by dashed lines. By thus setting up the cross connects using the switches 104 and 114, a path connecting between the respective RPR units 103 and 113 is formed, forming the ring-shaped network 206.
An RPR apparatus that can construct an RPR network without incorporating the L3 function is disclosed. This RPR apparatus includes a storage unit which stores mapping between an RPR apparatus address indicating each RPR apparatus connected to a ring and a user device address indicating a user device accommodated in each RPR apparatus, and when the RPR apparatus receives from a user device accommodated therein data addressed to some other user device, if the RPR apparatus address of the RPR apparatus accommodating that other user device is stored in the storage unit, the RPR apparatus transmits the data onto the RPR network by appending to it an RPR header in which that RPR apparatus address is set as the destination RPR apparatus address.
There is also disclosed a line accommodating apparatus wherein a plurality of optical interfaces 40 connected to a first communication system such as SONET and a plurality of stations 30 connected to a second communication system such as an RPR network 70 that uses the SONET as a communication medium are mounted in a shelf 10, and wherein the stations 30 and the optical interfaces 40 are connected via a path control unit 50. The stations 30, the optical interfaces 40, and the path control unit 50 are collectively controlled by an intelligent card 20, and when adding or deleting any station 30, the intelligent card 20 switches the connection path in the path control unit 50.
Related art is disclosed in International Publication Pamphlet No. WO2004/073262 and Japanese Laid-open Patent Publication No. 2006-279891.